// modifier can be removed with the 'REMOVE' operator.
operation.setOperator(Operator.ADD);
// Update ad group bid modifier.
AdGroupBidModifierReturnValue result =
bidModifierService.mutate(new AdGroupBidModifierOperation[] {operation});
for (AdGroupBidModifier bidModifierResult : result.getValue()) {
System.out.printf(
"Campaign ID '%d', AdGroup ID '%d' was updated with ad group level modifier: %.2f\n",
bidModifierResult.getCampaignId(), bidModifierResult.getAdGroupId(),
bidModifierResult.getBidModifier());